Chris Iannetta continued Saturday’s assault on Livan Hernandez at Coors Field with a fourth-inning home run. Iannetta had four hits and scored three runs. (Joe Mahoney/AP)

Livan Hernandez walked slowly off the mound before the sun set Saturday night over Coors Field, head down, carrying his red glove in his right hand. The Washington Nationals could once rely on Hernandez, no matter the outcome, chewing up innings and carrying them deep into his starts. Another early exit affirmed the end of those days.

In a 15-7 loss to the Colorado Rockies, Hernandez exited without recording an out past the fourth inning for the third time in five starts. He allowed nine runs, seven of them earned and two scoring on account of his own throwing error, before leaving with two outs in the fourth inning. The Nationals’ awakening offense lessened the final difference with a four-run rally in the sixth inning, but Hernandez created too deep a deficit.

Four relievers combined with Hernandez as the Nationals allowed their most runs in a game this season. Hernandez set the tone, continuing a history of struggles at Coors Field. Hernandez, who for part of 2008 pitched for the Rockies, has a 7.33 career ERA here. Hernandez relies on his bag of offspeed pitches, and in the high altitude they tend to spin and spin without moving.

“It’s difficult pitching here,” Hernandez said. “A pitcher like me, when you depend on the curveball sometimes, it’s tough. I throw curveball sometimes, and it breaks the other way. I can’t do nothing about it. I got to be ready for the next one.

“It was one of those days where you throw anything, and people hit it. You make a mistake in this park, and you’re going to pay for it.”

Hernandez surrendered nine hits, spotting the Rockies four runs in the third inning thanks partly because of his misplay on a sacrifice bunt and unraveling during a five-run fourth inning. The Nationals want to use the remainder of this season to provide major league experience to some of their top prospects. Their presence will require some starter to leave the rotation, and with his recent performance Hernandez has made himself a candidate.

“He wasn’t real sharp,” Manager Davey Johnson said. “His stuff wasn’t sharp. When he’s not on, bad things happen.”

Saturday night, Hernandez actually started strong, retiring six of the first seven hitters he faced. From then on, Hernandez found himself in constant trouble.

Chris Iannetta started the third inning with a single, and Hernandez made a major misstep when he hit pitcher Jhoulys Chacin with a pitch as Chacin squared to bunt. With men on first and second, Eric Young Jr. tried a sacrifice bunt, which was the moment Hernandez’s outing started to spiral.

Young dropped the bunt down to the left of the pitcher’s mound. Hernandez scooped the ball with his feet set as if he wanted to turn and throw to third, but Ryan Zimmerman had vacated the base charging in to field the bunt. Hernandez instead looked to first and lobbed an off-balance throw to Michael Morse. The ball bounced by him, scoring one run and creating a jam.

“I was trying to do something,” Hernandez said. “I don’t know what I was doing there. . . . I never make an error like that. It’s tough. I got a little frustrated there, because I never do that.”

Dexter Fowler smoked a slider into the left field corner for a triple, scoring two more runs. When Fowler scored on a sacrifice fly, the Nationals trailed, 4-0.

Hernandez’s start deteriorated further in the fourth. The Rockies nailed five hits, including home runs by Ty Wigginton and Iannetta. Johnson hoped to exhaust innings with the knowledge that Tyler Clippard would not be available following his two-inning stint Friday. But after Troy Tulowitzki’s two-out RBI single to center, he had no choice and pulled Hernandez.

The performance added to Hernandez’s recent sine-wave pattern. He has lasted four, six, four, six and 32 / 3 innings over his past five starts. In games started this season by Hernandez, their opening day starter, the Nationals are 7-17. He is beloved by teammates and fans, but it would be difficult to argue Hernandez is not the Nationals’ fourth- or fifth-best starter at the moment.

The Nationals stormed back with a furious, two-out rally in the seventh inning, started by the unlikeliest of hitters. After Rockies reliever Greg Reynolds retired the first two batters he faced, Tom Gorzelanny, having entered to relieve Hernandez, stepped to the plate batting right-handed, which he had not done all year.

Gorzelanny had dabbled in batting right-handed before in his career, and he plays golf and hockey right-handed. It’s comfortable. He was 1 for 25 left-handed this season, so “I just said, ‘Screw it,’ ” he said.

Sure enough, Gorzelanny bounced a single up the middle — his second hit this year in 26 at-bats.

The top of the Nationals’ order turned it into a meaningful hit. Rick Ankiel, one of Washington’s hottest hitters, followed by launching 1-2 change-up into the upper deck in right field. Ankiel’s fourth home run in a 27 at-bat span only started the rally.

Danny Espinosa smoked a double to left-center. Zimmerman, who in the first inning extended his hitting streak to 15 games, scored him with a double off the right-field fence, the fourth time he had reached base Saturday night. Morse followed with a single, giving him his third RBI and third hit of the night.

By the time Jayson Werth grounded out to end the rally, the Nationals had used five consecutive hits to trim a six-run deficit to 9-7. They did it predominantly with the top four hitters in their lineup, who went 9 for 17 with three walks. Morse added a single in the eighth, which made him 4 for 5 and raised his average to .327, third in the National League.

“I feel great about offense,” Johnson said. “We just need to get our pitching straightened out a little bit.”

The Nationals’ hope for a comeback ended quickly. Gorzelanny surrendered an RBI double to Tulowitzki, and Todd Coffey and Sean Burnett teamed up to allow three more runs in seventh inning. Henry Rodriguez, who Friday night allowed all four hitters he faced to reach base, yielded two more runs, one on a bases-loaded walk and the other on a wild pitch.

So, more people than Hernandez faltered for the Nationals, but for the third time in a month he was an impediment to victory. Hernandez for so long had been so reliable for the Nationals. As they figure out their rotation for the rest of the season, he lately has provided only another measure of uncertainty.